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1.
Acrosin is an important proteolytic enzyme that is capable of hydrolysing the zona pellucida in bovine oocyte. Lysophosphatydic acid (LPA) derivated from lysophosphatidylcholine (LPC) is known to trigger the acrosome exocytosis. The present study was aimed at examining the acrosin activity variations in LPC‐induced acrosome exocytosis and its regulation by tyrosine kinase, protein kinase C (PKC) and voltage‐dependent calcium channels (VDCC) in spermatozoa previously capacitated with heparin or quercetin. The enzyme activities were spectrophotometrically measured using N‐α‐benzoyl‐DL‐arginine p‐nitroanilide as an acrosin‐specific substrate. The capacitation and acrosomal reaction were evaluated by chlorotetracycline assay, and the viability and acrosome integrity were evaluated by the trypan blue stain/differential interference contrast. It was observed that LPC induced acrosome exocytosis and increased the activity of acrosin in spermatozoa previously capacitated with heparin. In heparin/LPC‐treated samples, it was observed that the inhibition of tyrosine kinase and PKC blocked the acrosome exocytosis and the acrosin activity (p < 0.05). Under these conditions, in heparin‐capacitated spermatozoa, the LPC provokes an acrosin activity increase that is independent of calcium influx through VDCC Type L. In cryopreserved bovine spermatozoa, LPC might require modulation, mainly tyrosine kinase participation with respect to PKC activity to induce acrosome exocytosis and increase acrosin activity.  相似文献   

2.
The present experiment was designed to determine the effects of various biologically active substances, such as oestradiol (OE), progesterone (P4) and heparin (Hep) alone or in combination on sperm plasma membrane scrambling, capacitation and acrosome reaction (AR) of post-thaw bovine spermatozoa. Spermatozoa were incubated for 180 min in capacitation medium supplemented with (i) 1 mug/ml OE; (ii) 1 mug/ml P4; (iii) 1 mug/ml OE and 1 mug/ml P4; (iv) 1 mug/ml OE and 5 mug/ml Hep; (v) 1 mug/ml P4 and 5 mug/ml Hep; (vi) 1 mug/ml OE, 1 mug/ml P4 and 5 mug/ml Hep. At predetermined time intervals aliquots were taken to assess sperm plasma membrane scrambling, or capacitation (AR induced by lysophosphatidylcholine) in spermatozoa. The second experiment was aimed to study the effects of OE, P4 and OE/P4 as potential inducers of AR in Hep-capacitated spermatozoa. Plasma membrane scrambling was assessed by a flow cytometer, using Merocyanine staining. Acrosomal status and viability of spermatozoa were evaluated under epifluorescence microscope with Ethidium homodimer-1/peanut agglutinin fluorescein isothiocyanate staining method (EthD-1/PNA-FITC). The results show that OE, P4 and a combination of OE/P4 at concentrations used did not affect sperm viability. Heparin significantly (p < 0.001) increased sperm plasma membrane scrambling of OE and P4-treated spermatozoa. P4 significantly affected the rate of sperm capacitation (p < 0.001) and AR (p < 0.05), but OE expressed membrane-stabilizing properties (p < 0.05). It can be concluded that in frozen-thawed bovine spermatozoa OE presents plasma membrane stabilizing properties that can be abolished by Hep, but not by P4. Progesterone possesses capacitating and AR-inducing properties in frozen-thawed bovine spermatozoa that can be alleviated by OE.  相似文献   

3.
The aim of this work was to study the effect of progesterone (P4) on capacitation and acrosome reaction (AR) of post-thaw bovine spermatozoa in vitro. Spermatozoa were incubated (0-180 min) in capacitation medium supplemented with 0, 0.1, 1.0 and 10.0 microg/ml of P4. At different time intervals aliquots were taken to determine sperm plasma membrane lipid destabilization, or capacitation (AR induced by lysophosphatidylcholine) in spermatozoa. The second experiment aimed to study the effects of P4, as potential inducer of AR in heparin-capacitated spermatozoa. The acrosomal status and viability of spermatozoa were evaluated under an epifluorescence microscope using Ethidium homodimer/peanut agglutinin fluorescein isothiocyanate staining method. Plasma membrane scrambling in spermatozoa was assessed by a flow cytometer, using merocyanine staining. The results show that P4 at the concentrations used had no negative effects on sperm viability. Progesterone significantly enhanced sperm capacitation (p < 0.001), but had no effect on plasma membrane lipid stability (p > 0.05) and did not significantly increase the AR of heparin-capacitated spermatozoa (p > 0.05). Progesterone displayed its effects in a dose-dependent manner with a maximum effect of 10 microg/ml P4 at 180 min of incubation. The results demonstrate that in cryopreserved bovine semen, P4 acts as capacitating, but not as an AR-inducing agent.  相似文献   

4.
The atomic force microscope (AFM) provides nanometer resolution, topographic data of the natural surface structure of materials. We studied the topology of the surface structure of bovine sperm heads during the acrosome reaction by AFM. In addition, we numerically analyzed the areas of the median sagittal plane of the sperm heads. Bovine frozen-thawed spermatozoa were washed, capacitated by heparin, and incubated with lysophosphatidylcholine (LPC) to induce the acrosome reaction, smeared on a cover glass, air-dried, and observed with AFM using the dynamic force (tapping) mode. AFM analysis of spermatozoa showed the clear surface structure of acrosomes, equatorial segments, postacrosomal regions and necks. Although AFM images of spermatozoa capacitated by heparin had complete acrosomes, most spermatozoa treated with LPC had no acrosomal caps as shown by AFM. These observations coincided with those obtained by light microscopy after staining with naphthol yellow S and erythrosin B. Furthermore, numerical analysis of AFM images indicated that areas of the median sagittal plane of the anterior portions of acrosome-reacted sperm heads (2679 +/- 616 pixels) were approximately 40% less than those of intact heads (4535 +/- 174 pixels, P<0.05). These results indicate that AFM can usefully observe and numerically analyze the fine surface structures of bovine spermatozoa.  相似文献   

5.
Mammalian sperm undergo a series of biochemical transformations in the female reproductive tract that are collectively known as capacitation. Cyclodextrins added to the sperm culture medium have been described to induce in vitro sperm capacitation, enabling its use in protein‐free media. However, the additive capacitating effect of methyl‐β‐cyclodextrin (MβCD) in the medium containing bovine serum albumin (BSA) is unknown in the bovine species. In this study, we evaluated the effects of incubating frozen–thawed bovine spermatozoa in a BSA‐containing medium supplemented with MβCD on different sperm quality and functional parameters. Sperm viability decreased with the addition of MβCD in a dose‐dependent manner (p < 0.05), and DNA damage could be observed but only with the highest concentration of MβCD. However, pre‐incubation of spermatozoa in MβCD‐supplemented medium improved the capacitation status as assessed by the increase in plasma membrane fluidity, intracellular calcium concentration, induced acrosome reactivity and zona pellucida (ZP)‐binding ability (p < 0.05). Thus, we conclude that MβCD supplementation is able to enhance the capacitation status of frozen–thawed bovine spermatozoa cultured in capacitation medium containing BSA and could result in a valid strategy for its application on artificial reproductive technologies such as in vitro fertilization or intracytoplasmic sperm injection.  相似文献   

6.
This study was designed to evaluate the effect of single layer centrifugation (SLC) and subsequent cold storage on stallion sperm capacitation‐like status and acrosome reaction. Three stallions were included in the study, with three ejaculates per stallion. The samples were examined 4, 24 and 72 h after collection, extension and SLC, with storage at 6°C. Sperm capacitation‐like status was investigated using the fluorescent dye chlortetracycline (CTC). There was no difference in capacitation‐like status between colloid‐selected and non‐selected spermatozoa. Sperm motility decreased significantly during cold storage, whereas the proportion of apparently capacitated spermatozoa increased. There was no change in the proportion of acrosome‐reacted spermatozoa. In conclusion, SLC through Androcoll?‐E does not adversely affect the capacitation‐like status of stallion spermatozoa, although it did increase with time during cold storage.  相似文献   

7.
Our aim was to evaluate the effect of Sephadex filtration on respiratory activity of porcine spermatozoa and its relation with quality and functional sperm parameters. Samples were evaluated regarding oxygen uptake and sperm parameters: motility, plasma and acrosome membrane integrity, capacitation and acrosome reaction induction in vitro, plasma membrane functionality, determined by the hypo‐osmotic swelling test (HOST), and lipid peroxidation assessed by thiobarbituric acid assay. Sephadex filtration improved all routine quality parameters (motility, plasma and acrosome membrane integrity) and functional parameters (HOST, in vitro capacitation and true acrosome reaction levels) and produced a significant decrease in cryocapacitation and lipid peroxidation. Oxygen uptake increased in Sephadex samples (41 ± 7%) respect to single washing. Oxygen addition of carbonyl‐cyanide‐m‐chlorophenylhydrazone (CCCP) confirmed mitochondrial coupling in washed and Sephadex samples; showing an increase of 2.6 and 4.2 times for oxygen consumption in single washing and Sephadex ones, respectively. The increase in oxygen uptake with succinate addition with respect to basal oxygen uptake was significantly lower in Sephadex samples (63 ± 25%) than in the washed ones (183 ± 35%). Sephadex samples showed higher mitochondrial activity measured by oxygen consumption and improved quality and functional parameters. Our study recommends this protocol due to the fact that this filtration method removes dead or damaged spermatozoa allowing to obtain cryopreserved boar spermatozoa with optimized fertilizing capacity.  相似文献   

8.
The present study was conducted to examine the effect of high heparin concentration on capacitation of buffalo spermatozoa with a short incubation time. Frozen thawed spermatozoa from three buffalo bulls were pooled and treated with either 50, 100 or 200 microg/ml heparin for 30 min. Capacitation was evaluated by acrosome reaction of spermatozoa and in vitro fertilization rate (per cent cleavage rate, per cent cleavage index). Acrosome reaction was induced in heparin treated spermatozoa with calcium ionophore A23187 and staining was carried out with Coomassie G-250 to evaluate the response as compared with control (0 heparin + calcium ionophore). Significantly higher percentage of acrosome reaction (AR) spermatozoa was noted after heparin treatment (36.8-48.2%) as compared with control (8.1% ; p < 0.05) but differences among the three heparin concentrations were non-significant. However, a significantly higher in vitro fertilization rate was recorded in spermatozoa capacitated by 50 and 100 microg/ml heparin (80.4 and 75.9% cleavage rate, respectively) as compared with 200 microg/ml heparin (47.2% cleavage rate; p < 0.001). It is concluded that buffalo spermatozoa capacitated with 50-100 microg/ml heparin had significantly higher ability to improve in vitro fertilization rate in buffalo.  相似文献   

9.
The aim of this work was to determine the enzymatic activity of phosphofructokinase (PFK), malate dehydrogenase (MDH) and isocitrate dehydrogenase (IDH) in boar spermatozoa and study their participation in bicarbonate‐induced capacitation and follicular fluid‐induced acrosome reaction. Enzymatic activity of these enzymes was determined spectrophotometrically in extracts of boar spermatozoa. Sperm suspensions were incubated in the presence of bicarbonate (40 mM), a well‐known capacitation inducer, or follicular fluid (30%), as an acrosome reaction inducer, and different concentrations of oxoglutarate, oxalomalate and hydroxymalonate, inhibitors of PFK, IDH and MDH, respectively. Capacitation percentages were determined by the fluorescence technique of chlortetracycline (CTC), and true acrosome reaction was determined by trypan blue and differential–interferential contrast, optical microscopy. The activity of PFK in boar spermatozoa enzymatic extracts was 1.70 ± 0.19 U/1010 spermatozoa, the activity of NAD‐ and NADP‐dependent IDH was 0.111 ± 0.005 U/1010 and 2.22 ± 0.14 U/1010 spermatozoa, respectively, and the activity of MDH was 4.24 ± 0.38 U/1010 spermatozoa. The addition of the specific inhibitors of these enzymes prevented sperm capacitation and decreased sperm motility during capacitation and inhibited the acrosome reaction (AR), without affecting the sperm motility during this process. Our results demonstrate the participation of PFK, IDH and MDH in bicarbonate‐induced capacitation and follicular fluid‐induced acrosome reaction in boar spermatozoa, contributing to elucidate the mechanisms that produce energy necessary for these processes in porcine spermatozoa.  相似文献   

10.
用台盼兰—姬姆萨染色检测家畜精子顶导反应的研究   总被引：1，自引：0，他引：1  
本文探讨了用台盼兰—姬姆萨染色检测家畜精子顶体反应的可行性。用肝素或钙离子载体诱发精子顶体反应。根据染色结果将精子分为四类:a)核后帽部不着色或淡青色,顶体不着色或部分紫红色(有顶体反应活精子);b)核后帽部暗青色.顶体部不着色或部分暗红色(有顶体反应死精子);c)核后帽部不着色或淡青色,顶体部紫红色(无顶体反应活精子);d)核后帽部暗青色,顶体部暗紫红色(无顶体反应死精子)。有顶体反应活精子百分率与仓鼠卵穿透率呈强正相关。从而证明台盼兰—姬姆萨染色是检测家畜精子顶体反应的有效手段,并能预测获能处理后精子的受精能力。  相似文献   

11.
When released into an appropriate environment, mammalian spermatozoa begin to capacitate and then continue until fully capacitated and able to fertilize. During capacitation in vitro, some cells 'over-capacitate' and undergo spontaneous acrosome reactions; this would be highly undesirable in vivo since already acrosome-reacted spermatozoa are non-fertilizing. Recent studies have revealed that seminal plasma contains several small molecules that bind to specific receptors on the sperm plasma membrane and act as 'first messengers', causing biologically important changes in availability of the 'second messenger' cAMP. Fertilization promoting peptide (FPP), calcitonin and adenosine all regulate cAMP production, stimulating it in uncapacitated spermatozoa and then inhibiting it in capacitated cells; in contrast, angiotensin II stimulates cAMP throughout capacitation. The molecules that regulate cAMP appear to do so via G protein-modulated changes in membrane associated adenylyl cyclases (mACs). Both mouse and human spermatozoa have been shown to have Galphas and Galphai2, as well as several isoforms of mAC, located in the same regions as the specific receptors. Thus spermatozoa possess the required elements for several separate signal transduction pathways, many of which regulate mAC/cAMP and so maintain sperm fertilizing ability. In vivo, such responses could increase the chances of successful fertilization.  相似文献   

12.
To evaluate effects of different concentrations of pentoxifylline, as phosphodiesterase inhibitor, on quality of motility, capacitation and acrosome reaction, Ejaculated spermatozoa were collected from crossbred dogs. The sperm were incubated at concentrations of 0.1, 1, 10 and 100 mM pentoxifylline for 2 h. Conventional assessment was also made on the percentage of motility and quality of motility of spermatozoa; values were expressed as sperm motility index (SMI). Capacitation and acrosome reaction were also evaluated by chlortetracycline fluorescence staining. SMI as quality index of sperm was significantly increased in concentrations of 10 and 100 mM pentoxifylline during 1 and 2 h compared to control. The number of capacitated or acrosome reacted spermatozoa significantly (P < 0.05) were higher than controls at high concentrations of pentoxifylline (10 and 100 mM) during 1 and 2 h. In conclusion, high concentration of pentoxifylline is able to induce capacitation and acrosome reaction and improves quality of motility in canine ejaculated spermatozoa.  相似文献   

13.
海藻糖对猪精液冷冻保存效果的影响   总被引：8，自引：0，他引：8  
在传统的Tris-柠檬酸-葡萄糖稀释液基础上，分别添加25％、50％、75％、100％的海藻糖，研究不同浓度海藻糖对猪精液冷冻后精子质量的影响。结果表明，海藻糖相对于对照TCG稀释液能够显著改善和提高猪精液的冷冻效果，其最佳添加浓度为25％，冷冻-解冻后猪精子活力、活率、线粒体活性、质膜完整性以及顶体完整率均显著提高（P〈0．05），分别达到41．38％、46．34％、44．56％、43．51％和64．09％。海藻糖可以明显抑制精子获能，获能处理前精子获能率仅为3．68％，而获能处理后达到41．82％，有利于促进精子获能。精液稀释液中甘油的适宜添加浓度为2％，海藻糖只有与甘油共同作用，才能在冷冻-解冻过程更加有效地保护精子。猪精子活力、活率、线粒体活性、质膜完整率、顶体完整率等之间存在极显著的正相关关系（P〈0．01），而与获能处理前精子的获能率存在显著的负相关关系（P〈0．05）。  相似文献   

14.
The purpose of this study was to evaluate the ability of various chemicals to induce capacitation of stallion spermatozoa using 2 different assay systems. In Experiment 1, freshly ejaculated spermatozoa were treated for 0, 3 and 6 h with 10 μ g/ml heparin, 0.5 mM hypotaurine or 5 mM caffeine, or were incubated for 0, 3 and 6 h following 1 min exposure to 0.1 μ M ionophore A23187. The acrosome reaction (AR) in the capacitated spermatozoa was induced by 15 min challenge with 100 μ g/ml lysophosphatidylcholine (LPC). In the BO/BSA-control medium (Brackett and Oliphant medium with 0.3% BSA), mean percentage of AR spermatozoa at 0 h was 30%, and the AR rates increased to 40 and 48% after 3 and 6 h incubation, respectively. There was no significant further increase of the AR rates in the spermatozoa treated with heparin (50% at 6 h) and hypotaurine (58% at 6 h) when compared to the control. Caffeine had a beneficial effect on inducing sperm capacitation after 3 and 6 h incubation (AR rates; 61 and 66%, respectively, P<0.01). Immediately after ionophore A23187 treatment, the AR rate increased to 56%, and reached 68 and 67% after 3 and 6 h incubation, respectively (P<0.01). Spermatozoal motility at any time points did not differ between control and any chemical treatment groups, except one treatment (ionophore; 3 h group).In Experiment 2, frozen-thawed spermatozoa were treated with 4 different chemicals as described above. Aliquot of spermatozoa was added to a microdrop of BO/BSA medium in which 6 to 10 in vitro-matured, zona-free mare oocytes were placed, and the oocytes were fixed and stained 20 h after insemination. The penetration rate by BO/BSA-treated spermatozoa was 76%, which was comparable to the results with heparin (73%), hypotaurine (78%) and caffeine (58%). In contrast, treatment of spermatozoa with ionophore A23187 gave a significantly lower penetration rate (30%) than the control value. Surprisingly these two experiments had different conclusions in assessing capacitation of stallion spermatozoa.  相似文献   

15.
Twenty ejaculates from five dairy AI‐bulls were used to compare, in a split‐sample experiment, the fertility [56 day‐non‐return‐rate (NRR) from more than 14000 AI) and sperm viability post‐thaw of semen diluted with an egg yolk‐ (Triladyl®) or soybean‐based (Biociphos‐Plus®) commercial extender. The in vitro evaluations were divided in two experiments. Experiment 1 (n = 20) included post‐thaw evaluations of motility (subjective and computerized), membrane integrity (CalceinAM/EthD‐1, SYBR‐14/PI, and osmotic resistance test; ORT), and capacitation status (CTC/EthD‐1). Experiment 2 (n = 10) included evaluations of the capacitation‐(CTC/EthD‐1) and acrosome status (FITC‐PSA/EthD‐1) during incubation with/without a challenge with solubilized zona pellucida proteins (SZP). No significant difference in the fertility (69.1 ± 0.8 versus 69.2 ± 0.8) results was found between the two extenders. In experiment 1, the computerized motility evaluations post‐thaw (CASA) showed higher values for Biociphos‐Plus® processed semen for the velocity patterns and lateral sperm head displacement. After 6 h at room temperature (20–22°C) all the CASA motility patterns were significantly higher for Biociphos‐Plus®. The proportion of spermatozoa with intact membranes assessed by CalceinAM was significantly higher in Biociphos‐Plus® (p < 0.001) compared to Triladyl®, but such difference was not seen when using SYBR‐14 or the ORT‐assay. When using the CTC/EthD‐1 assay, a lower proportion of acrosome reacted (AR) spermatozoa post‐thaw (p < 0.01) was found in Biociphos‐Plus® processed semen, as well as a tendency (p < 0.07) for a higher number of uncapacitated spermatozoa. In experiment 2, the proportion of uncapacitated spermatozoa was significantly higher for Biociphos‐Plus® when semen was incubated (38°C and 5% CO2) without SZP at both 0 (p < 0.001) and 30 min (p < 0.05). Concomitantly, Triladyl® showed a higher percentage of capacitated spermatozoa at 0 (p < 0.01), 30 (p < 0.05) and 120 min (p < 0.05). A higher (p < 0.05) incidence of AR‐spermatozoa was seen in Triladyl® at the beginning of the incubation with SZP. No significant difference between extenders was detected for the acrosome status by the FITC‐PSA‐assay. Incubation with SZP induced acrosome reaction of capacitated spermatozoa in both extenders, which was detected by CTC and FITC‐PSA assays. In conclusion, fertility was not affected by Biociphos‐Plus® when 15 × 106 of spermatozoa per AI dose were inseminated. The finding that higher frequencies of spermatozoa seemed more membrane stable post‐thaw, when frozen in Biociphos‐Plus®, might indicate that this extender better protects the sperm viability compared with Triladyl®.  相似文献   

16.
Capacitation is a biological phenomenon occurring prior to fertilization and is a multiple event process. Many physiological and biochemical changes takes place during the process; these changes are related to lipid composition of membrane, intracellular modulation of ion concentration, protein phosphorylation, sperm movement and membrane permeability. These events occur when the sperm is exposed to the new environment of ion concentration in the female reproductive tract. Ions such as bicarbonate and calcium facilitate capacitation by activating adenylyl cyclase, thus initiating protein kinase A (PKA) signalling cascade. Extracellular‐regulated kinase pathway is activated by ligand binding to the membrane receptors and intracellular activation by reactive oxygen species (ROS). Activation of these pathways leads to the phosphorylation of different proteins, which is associated with events such as capacitation, hyperactivation and acrosome reaction that are essential for successful fertilization. Extensive studies were carried out on protein phosphorylation in relation to capacitation, but its role still remains ambiguous.  相似文献   

17.
In this study, the relations between fertility (56‐day non‐return rates, 56‐day NRR) after artificial insemination (AI) and bull sperm characteristics post‐thaw, after swim‐up and after co‐incubation with heparin (Hep) and hyaluronan (HA), respectively, were determined, attempting to determine if such a procedure could be of value to evaluate the potential fertilizing ability of frozen‐thawed AI bull spermatozoa. Spermatozoa from 20 semen batches derived from 20 Swedish Red and White AI bulls ranging widely in their field fertility after AI (55–79% 56‐day NRRs) were evaluated with regards to post‐thaw motility, membrane integrity, and migration through a simple swim‐up procedure. Sperm viability and capacitation status were evaluated by two different vital staining procedures and chlortetracycline hydrochloride staining. Sperm motility and membrane integrity post‐thaw (e.g. indicators of sperm viability) were significantly correlated (r = 0.53, p < 0.05 and r = 0.59, p < 0.01, respectively) with fertility. Heparin (5 µg/ml) significantly (p lt; 0.001) increased the frequencies of capacitation and acrosome‐reaction (AR) among swim‐up separated spermatozoa, whereas HA at a concentration of 50 ng/ml did not have any significant capacitating effect. The incidences of capacitated or AR‐spermatozoa following Hep‐treatment were not correlated with fertility. On the other hand, the percentage of viable spermatozoa was significantly (p < 0.001) lower in Hep‐treated samples than in control and HA‐treated samples and was significantly (r = 0.49, p < 0.05) correlated with fertility after AI (56‐day NRR). The results indicate that the percentage of viable spermatozoa after swim‐up separation and heparin‐exposure from a selected population of AI bulls were significantly and positively related to the AI fertility of the donors and thus could be used as a parameter to determine the fertilizing ability of frozen—thawed AI bull spermatozoa.  相似文献   

18.
The aim of this work was to quantify NO, O2? and ONOO? production during heparin‐induced capacitation of cryopreserved bovine spermatozoa. A time dependent hyperbolic increase was observed for heparin‐dependent capacitation, O2 uptake, and NO production. Conversely, O2? production was increased during the first 15 min of incubation, showing a decrease from this time until 45 min. At 15 min of heparin incubation, a threefold increase in O2 consumption (5.9 ± 0.6 nmol/min × 107 cells), an enhancement in NO release (1.1 ± 0.2 nmol/min × 107 cells), and a five‐fold increase in O2? production (1.3 ± 0.07 nmol/min × 107 cells), were observed. Peroxynitrite production rate was estimated taking into account NO and O2? generation and the second‐order rate constant of the reaction between these species. To conclude, heparin‐induced capacitation of cryopreserved bovine spermatozoa activates (i) mitochondrial O2 uptake by high ADP levels due to increased energy requirements, (ii) NO production by a constitutive NOS and (iii) O2? production by a membrane‐bound NAD(P)H oxidase. The products of both enzymes are released to the extracellular space and could be involved in the process of sperm capacitation.  相似文献   

19.
应用透射电镜技术,对牛精子体外获能前后超微结构观察的结果表明,牛精子的超微结构相似于其他哺乳动物,但顶体较大;获能后精子发生了顶体反应.在顶体反应中,囊泡化有3种形式:(1)顶体外膜相互融合,形成囊泡;(2)顶体外膜内陷形成囊泡化;(3)顶体外膜和质膜融合形成囊泡.此外,对精子的结构特点和囊泡形成过程进行了讨论.  相似文献   

20.
It is not until accomplishment of a variety of molecular changes during the transit through the female reproductive tract that mammalian spermatozoa are capable of exhibiting highly activated motility with asymmetric whiplash beating of the flagella (hyperactivation) and undergoing acrosomal exocytosis in the head (acrosome reaction). These molecular changes of the spermatozoa are collectively termed capacitation and promoted by bicarbonate, calcium and cholesterol acceptors. Such capacitation-promoting factors can stimulate intracellular cyclic AMP (cAMP) signal transduction in the spermatozoa. Meanwhile, hyperactivation and the acrosome reaction are essential to sperm fertilization with oocytes and are apparently triggered by a sufficient increase of intracellular Ca2+ in the sperm flagellum and head, respectively. Thus, it is necessary to investigate the relationship between cAMP signal transduction and calcium signaling cascades in the spermatozoa for the purpose of understanding the molecular basis of capacitation. In this review, I cover updated insights regarding intracellular cAMP signal transduction, the acrosome reaction and flagellar motility in mammalian spermatozoa and then account for possible roles of intracellular cAMP signal transduction in the capacitation and subsequent hyperactivation of mouse and boar spermatozoa.  相似文献   

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